Test 1

1. Given that the key is 25, with the user of Caesar cipher, encrypt the following letters (6 Marks)

1. C
2. I 
3. P 
4. H 
5. E 
6. R

 

2. The plaintext “cryptography” is converted into the ciphertext “fubswrjudskb” by using the Caesar cipher. 

a) Determine the possible key.  (4 Marks)

( 10 marks)

 

3. In a public-key system using RSA, you intercept the ciphertext C = 10 sent to a user whose public key is e = 5, n = 35. What is the plaintext M?

(10 Marks)

 

4. The OSI security architecture consist of security services, mechanisms, and attacks. Explain the security services and mechanisms.
 

'7 12 201 b. Given the key, K = 5 17 22 encrypt the plaintext using the hill cipher. 4 16 21